Chediak-Higashi syndrome (CHS) and Hermansky-Pudlak syndrome (HPS) are fatal human genetic disorders characterized by structural and functional defects of multiple cytoplasmis organelles -- melanosomes, Iysosomes, and granules. We have cloned the genes for both CHS and HPS and are currently preparing antisera to the corresponding proteins. We wish to define the intracellular location of the CHS and HPS proteins (which are entirely novel), in both normal and mutant cells, and to determine whetha these proteins interact with each otha and with otha cellular components. We will immunostain tissue samples using our antisera and determine cellular localization of CHS and HPS using the confocal microscope at the IMR. These studies should help elucidate the pathogenesis of these disorders and thus guide eventual design of rational thaapies.